WHEEL ASSEMBLY

Abstract: A wheel assembly comprising a plurality of wheel segments (11) releasably fastened onto an inner structure (13). Each wheel segment (11) includes a rim segment (21) and a tyre segment (23) on the rim segment. The rim segments (21) are individually fastened onto the inner structure (13) in any suitable way such as by bolts (37). The assembly of wheel segments (11) and the inner structure (13) provide a rim (17) and a tyre (19) on the rim.

Description: TITLE Wheel Assembly TECHNICAL FIELD This invention relates to a wheel assembly for vehicles and to wheel elements which can be assembled around and inner structure to provide such a wheel assembly. BACKGROUND OF THE INVENTION The invention is particularly concerned with wheels having non-pneumatic tyres. There have been various proposals for non-pneumatic tyres for vehicles in which a resilient covering is fitted around a rim. Typical examples of such wheels are disclosed in various patents including US 1421029 (Row), US 1458844 (Lang), US 1553018 (Barth), US 5154490 (Burns), US 806738 (Rollinson) and GB 207632 (Blakey). With such wheels, the tyres comprise a plurality of resilient segments which are assembled on a rim comprising an outer rim portion surrounding an inner structure. The segments are releasably fastened to the rim by releasably fastening means. In many cases, the releasable fastening means are of a somewhat complicated construction which does not facilitate easy attachment of the segments onto, and easy removal of the segments from, the rim. Furthermore, the inner regions of the segment need to have sufficient strength in order to withstand shear forces and other loadings applied to them during operation of the wheel. This may require reinforcement in the form of thickening of the segments in the inner region with the result that additional material is used in the production of the segments, so increasing the cost of production and the mass of the segments. Bonding of the tyre segments onto the rim would avoid the need to have the reinforcement in the inner region of the segments but would remove the advantage of the segments being easily removable on an individual basis for repair or replacement. The rims employed with such wheels typically comprise an outer rigid band supported on an inner portion such as a disc having provision for mounting onto a wheel axle. The outer band is generally welded onto the inner portion. While this arrangement provides a rim which performs satisfactorily, it does have several disadvantages. One such disadvantage is that the rim is not necessarily compact for storage purposes prior to assembly of the wheel. A further disadvantage is that the rim usually cannot be repaired in the event of damage without first having to remove it from the vehicle to which it is fitted. Additionally, it is usually necessary to replace the rim portion in the event of damage to it. SUMMARY OF THE INVENTION It would be advantageous to have a wheel in which the rim has various parts which can be individually replaced in the event of damage. It would also be advantageous to have a wheel in which the tyre is provided by a plurality of segments bonded onto a rigid base. It would be further advantageous for the rigid base to provide part of the rim onto which the tyre is fitted. Various aspects of the present invention seek to provide a wheel assembly having one or more of the advantages referred to above. According to one aspect of the invention there is provided a wheel assembly comprising a rim having an axis of rotation and a tyre on the rim, wherein the rim comprises a plurality of rim segments detachably fastened onto an inner structure. Preferably, the rim segments are individually fastened onto the inner structure. The tyre may comprise a plurality of resilient tyre segments each fastened onto one of the rim segments. Conveniently, there is only one tyre segment on each rim segment. Each segment may be permanently or releasably fastened onto the respective rim segment. Conveniently, each tyre segment is permanently fastened onto its respective rim segment by being bonded thereto. The tyre segments may be configured to interlock one with another in the wheel assembly. Each rim segment may comprise an outer portion and an inner portion fixed to the outer portion, the outer portion presenting an outer locating face onto which the tyre locates. The locating face is preferably arcuate, the centre of curvature being coincident with the axis of rotation of the rim. The inner portion of the rim segment may comprise a mounting flange extending inwardly from the outer portion. The mounting flange may have a mounting face for bearing against the inner structure, the mounting face being substantially normal to the locating face presented by the outer portion. Each tyre segment may comprise a body having an outer portion supported on a plurality of spaced apart load-bearing ribs adapted to resiliently deflect under load. The body may have at least one aperture formed therein opening onto the exterior thereof, each aperture providing the spacing between neighbouring ribs. The body may be formed of resiliently deflectable material such as rubber. According to another aspect of the invention there is provided a wheel segment comprising a rim segment adapted to be releasably fastened on an inner structure, and a tyre segment on the rim segment. The tyre segment may be permanently or releasably fixed onto the rim segment. The rim segment may be adapted to be individually fastened onto the support structure. According to a third aspect of the invention there is provided a wheel assembly comprising a rim having an axis of rotation and a tyre on the rim, the tyre comprising a plurality of tyre segments bonded onto the rim. In the wheel assembly according to the third aspect of the invention, each tyre segment may comprise a body having an outer portion supported on a plurality of spaced apart load-bearing ribs adapted to resiliently deflect under load. The body may have at least one aperture formed therein opening onto the exterior thereof, each aperture providing the spacing between neighbouring ribs. The rim preferably comprises a plurality of rim segments, there being at least one tyre segment bonded onto each rim segment. The rim segments are preferably of a construction set forth hereinbefore. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which: Fig. 1 is a schematic perspective view of a wheel assembly according to the first embodiment and comprising a plurality of wheel segments one of which is removed to show the inner portion of the wheel assembly; Fig. 2 is a perspective view of an assembly of the wheel segments; Fig. 3 is a perspective view of one wheel segment viewed from the outer side thereof; Fig. 4 is a perspective view of the segment of Fig. 3 viewed from the inner side thereof; Fig. 5 is a side view of the wheel segment of Fig. 3; Fig. 6 is a cross-sectional view of the wheel segment of Fig. 3; Fig. 7 is a side view of two wheel segments which can be assembled to form a wheel assembly according to a second embodiment; Fig. 8 is a perspective view of a wheel segment which can be assembled along with other such wheel segments to provide a wheel assembly according to a third embodiment; and Fig. 9 is a cross-sectional view of a wheel segment according to a fourth embodiment. MODES OF PERFORMING INVENTION The various embodiments shown in the drawings are each directed to a wheel for a vehicle for use in industrial applications such as forklifts where high load-carrying capacity is required in a compact size with a continuous rolling radius to provide a smooth ride. Referring now to Figs. 1 to 6, the wheel assembly according to the first embodiment comprises a plurality of wheel segments 11 mounted onto an inner structure 13. The inner structure 13 is in the form of a disc having means 15 provided at its inner region for mounting onto the axle of a vehicle. A plurality of spaced mounting apertures 16 are provided around the outer region of the disc. The wheel segments 11 are each adapted to be releasably fastened onto the disc 13 to provide the wheel assembly with a rim 17 and a tyre 19 on the rim. Each wheel segment 11 comprises a rim segment 21 and a tyre segment 23. The rim segment 21 is substantially rigid and comprises an outer portion 25 presenting a curved outer locating face 26. The centre of curvature of the curved locating face 26 is coincident with the axis of rotation of the wheel. The outer portion 25 has a pair of longitudinal sides 27 extending between leading and trailing ends 28 and 29 respectively. The rim segment 21 also comprises an inner portion 30 which provides a mounting flange 31 having a mounting face 33 which is substantially normal to the locating face 26 and which is adapted to bear against the outer peripheral side region of the disc 13. The mounting flange 31 is provided with a plurality of mounting apertures 35, there being two such apertures in this embodiment. The apertures 35 register with corresponding apertures 16 formed in the disc 13 to receive mounting bolts 37 which releasably fasten the wheel segment 11 to the disc 13. When the wheel segments 11 are assembled onto the disc 13, the rim segments 21 in combination with the inner structure 23 provides the rim 17 for the wheel. The tyre segment 23 on each wheel segment 11 comprises a body 41 of resilient material such as rubber or some other suitable elastomeric material. The body 41 comprises an inner portion 43 having an inner face 45 for engagement with the locating face 26 of the rim segment 21, and an outer portion 47 spaced from the inner portion. The outer portion is relatively thicker than the inner portion. A plurality of load supporting ribs 49 extend between the inner and outer portions. The ribs 49 are in spaced apart relationship to define apertures 50 therebetween which extend through the body and open onto the side faces 53 thereof. The apertures 50 each comprise two lateral sections 51 one to each side of the centre of the tyre. The two lateral sections are inclined in opposite directions with respect to each other and merge at said centre. With this arrangement of the apertures 50, the ribs 49 defined between the apertures also have two lateral sections 54 only one of which is apparent in the drawings and which are inclined in opposite directions to extend inwardly and forwardly to merge at apex 56. In other words, the ribs are of a substantially V-formation. The body has two spaced apart end faces between which the side faces 53 extend, being a leading end face 57 and a trailing end face 58. The leading and trailing end faces 57, 58 are adapted to interengage with complementary faces on neighbouring elements to provide lateral stability and avoid twisting. The leading face 57 is of male formation, comprising a pair of opposed surfaces 61 which extend forwardly and inwardly to an apex 63. The trailing face 58 of a female formation to receive the male formation 57 and comprises a pair of opposed surfaces 65 which extend forwardly and inwardly to an apex 67. Engagement between the end faces 57, 58 of neighbouring tyre segments 23 provide mutual support for the tyre segments as they deflect under load. The leading and trailing ends 28, 29 of the outer portion 26 of the rim segment 21 are of complementary shape to the adjacent ends 57, 58 of the tyre segment 23. The sides and end of the tyre segment 23 overhang the sides and ends of the outer portion of the rim segment 21. The overhang of the sides affords protection to the rim segments 21 when the wheel assembly is used in an aggressive environment such as harsh terrain. The outer portion 47 of each tyre segment 23 presents an outer surface 71 which in combination with corresponding surfaces on the other tyre segments provides a running surface for the tyre 19. The outer surface 71 is a ground engaging surface which has a tread formation 73 provided with a series of axially spaced apart grooves 75 and a series of circumferential spaced grooves 77. The axially spaced grooves 75 are of a V-formation which corresponds to the V-formation of the load-supporting ribs 49. Each one of the grooves 75 is in alignment with one of the ribs 49 so as to assist in directing ground engaging loads to the rib. The spacing between the grooves 75 is such that part of one groove 75 lies within the confines of a neighbouring groove 75 so as to provide the tyre with a substantially constant rolling radius by insuring that some portion of the outer surface 35 is always in contact with the ground at all times. The wheel assembly according to the embodiment is particularly convenient to assembly. All that is required is to bolt the various wheel segments 11 onto the inner structure 13. If any one of the tyre segments 23 becomes damaged, it can be replaced relatively easily and simply by removing the corresponding wheel segment from the disc and replacing it with another. Similarly, if any one of the rim segments 21 becomes damaged, it too can be replaced simply by replacing the corresponding wheel segment. If desired, the rim segments 21 can be formed of a size and shape to interlock one with another in a similar manner to the tyre segments 23. While in this embodiment, the tyre segment 23 and rim segment 21 are of such relative sizes that the inner face 45 of the tyre segment overhangs the locating face 26 of the rim segment, it is possible in other embodiments (not shown) for the two faces 26, 45 to be substantially the same size such that there is littie or no overhang. Referring now to Fig. 7 of the drawings, the wheel assembly according to the second embodiment is similar to that of the first embodiment except that the end faces 57, 58 of each tyre segment 23 are configured to interlock in a manner which restricts radial movement of one tyre segment with respect to the other. The interlocking arrangement is provided by a male formation 81 at the leading end and a corresponding female formation 83 at the trailing end. The male and female portions 81, 83 each have a curved surface 85 centred on an axis generally parallel to the axis of rotation of the tyre. In this embodiment, the apertures 50 are elongated in the circumferential direction of the tyre with the result that the circumferential length of the aperture is greater than the radial height of the aperture. A further feature of the wheel assembly according to this embodiment is that the adjacent ends of the rim segments 21 are adapted to abut one another at 87. The embodiment shown in Fig. 8 of the drawings is similar to the earlier embodiments with the exception that the tyre segment is formed with apertures 91 which extend circumferentially, as opposed to transversely, of the rolling direction of the tyre. In this embodiment there are two such apertures with the result that the tyre segment has an inner portion 93, an outer portion 95 spaced from the inner portion and three circumferential load-supporting ribs 97 extending between the inner and outer portions. Referring now to Fig. 9 of the drawings, the embodiment shown therein is similar to the first embodiment with the exception that the tyre segment 23 has no inner portion with the result that the load supporting ribs 49 are bonded at their inner ends directly onto the locating face the rib segment 21. From the foregoing, it is evident that the present invention provides a wheel assembly which is of simple construction and which allows the wheel segments to be individually replaced as is necessary, such as in circumstances where the tyre segment and/or the rim segment becomes damaged. The manner of construction facilitates easily assembly of the wheels and also allows the wheel segments to be replaced without requiring the wheel to be removed from a vehicle onto which it is fitted. When the tyre becomes worn, the tyre segments can be removed from the rim segments and new tyre segments bonded onto the rim segments. The worn tyre segment can be removed from the rim segment in any suitable way and replaced with another tyre segment. Because the tyre segments are each bonded onto one of the rim segments they do not require reinforcement at the inner portion thereof with the result that the inner portion can be relatively thin in comparison to the outer portion. This provides a saving in the quantity of material used in the production of the tyre segment, as well as a slight reduction in weight. While the various embodiments have been described in relation to wheel assemblies in which the tyre segments are bonded onto the rim segments, it would be appreciated that the wheel segments can be constructed such that the tyre segments are releasably mounted onto the rim segments for convenient replacement. It should be appreciated also that the scope of the invention is not limited to the scope of the various embodiments described.

Claims: THE CLAIMS defining the invention are as follows:- 1. A wheel assembly comprising a rim having an axis of rotation and a tyre on the rim, wherein the rim comprises a plurality of rim segments detachably fastened onto an inner structure. 2. A wheel assembly according to claim 1 wherein the rim segments are individually fastened onto the inner structure. 3. A wheel assembly according to claim 1 or 2 wherein the tyre comprises a plurality of resilient tyre segments each fastened onto one of the rim segments. 4. A wheel assembly according to claim 3 wherein there is only one tyre segment on each rim segment. 5. A wheel assembly according to any one of the preceding claims wherein each tyre segment is permanently fastened onto the respective rim segment. 6. A wheel assembly according to claim 5 wherein each tyre segment is permanently fastened onto its respective rim segment by being bonded thereto. 7. A wheel assembly according to any one of claims 1 to 4 wherein each tyre segment is releasably fastened onto the respective rim segment. 8. A wheel assembly according to any one of the preceding claims wherein the rim segment comprises an outer portion and an inner portion fixed to the outer portion, the outer portion presenting an outer locating face onto which the tyre locates. 9. A wheel assembly according to claim 8 wherein the locating face is arcuate, the centre of curvature being coincident with the axis of rotation of the rim. 10. A wheel assembly according to claim 8 or 9 wherein the inner portion of the rim segment comprises a mounting flange extending inwardly from the outer portion. 11. A wheel assembly according to claim 10 wherein the mounting flange has a mounting face for bearing against and attachment to the inner structure, the mounting face being substantially normal to the locating face presented by the outer portion. 12. A wheel assembly according to any one of the preceding claims wherein tyre segments are configured to interlock one with another in the wheel assembly. 13. A wheel assembly according to any one of the preceding claims wherein each tyre segment comprises a body having an outer portion supported on a plurality of spaced apart load-bearing ribs adapted to resiliently deflect under load. 14. A wheel assembly according to claim 13 wherein the body has at least one aperture formed therein opening onto the exterior thereof, each aperture providing the spacing between neighbouring ribs. 15. A wheel assembly according to claim 13 or 14 wherein the tyre portion further comprises an inner portion spaced inwardly from the outer portion, the load-bearing rib being positioned between the inner and outer portions, the inner portion having an inner face located on the locating face. 16. A wheel assembly according to any one of the preceding claims wherein the rim segments are configured to interlock on with another in the wheel assembly. 17. A wheel segment comprising a rim segment adapted to be releasably fastened on an inner structure, and a tyre segment on the rim segment. 18. A wheel segment according to claim 7 wherein the rim segment is adapted to be fastened onto the inner structure. 19. A wheel segment according to claim 17 or 18 wherein the tyre segment is permanently fastened onto the respective rim segment. 20. A wheel segment according to claim 19 wherein each tyre segment is permanently fastened onto its respective rim segment by being bonded thereto. 21. A wheel segment according to claim 17 or 18 wherein each tyre segment is releasably fastened onto the respective rim segment. 22. A wheel segment according to any one of claims 17 to 20 wherein the rim segment comprises an outer portion and an inner portion fixed to the outer portion, the outer portion presenting an outer locating face onto which the tyre locates. 23. A wheel segment according to claim 22 wherein the locating face is arcuate, the centre of curvature being coincident with the axis of rotation of the rim. 24. A wheel segment according to claim 23 or 23 wherein the inner portion of the rim segment comprises a mounting flange extending inwardly from the outer portion. 25. A wheel segment according to claim 24 wherein the mounting flange has a mounting face for bearing against and attachment to the inner structure, the mounting face being substantially normal to the locating face presented by the outer portion. 26. A wheel segment according to any one of claims 17 to 25 wherein the tyre segment is configured to interlock with neighbouring segments in an assembly of the wheel segments. 27. A wheel segment according to any one of claims 17 to 26 wherein the tyre segment comprises a body having an outer portion supported on a plurality of spaced apart load-bearing ribs adapted to resiliently deflect under load. 28. A wheel segment according to claim 27 wherein the body has at least one aperture formed therein opening onto the exterior thereof, each aperture providing the spacing between neighbouring ribs. 29. A wheel segment according to any one of the preceding claims wherein the rim segment is configured to interlock neighbouring rim segments in an assembly of the wheel segments. 30. A wheel assembly comprising a rim having an axis of rotation and a tyre on the rim, the tyre comprising a plurality of tyre segments bonded onto the rim. 31. A wheel assembly according to claim 30 wherein tyre segments are configured to interlock one with another in the wheel assembly. 32. A wheel assembly according to claim 30 or 31 wherein each tyre segment comprises a body having an outer portion supported on a plurality of spaced apart load-bearing ribs adapted to resiliently deflect under load. 33. A wheel assembly according to claim 32 wherein the body has at least one aperture formed therein opening onto the exterior thereof, each aperture providing the spacing between neighbouring ribs. 34. A wheel assembly according to any one of claims 30 to 33 wherein the tyre portion further comprises an inner portion spaced inwardly from the outer portion, the load-bearing ribs being positioned between the inner and outer portions, the inner portion having an inner face located on the locating face. 35. A wheel assembly substantially as herein described with reference to the accompanying drawings. 36. A wheel segment substantially as herein described with reference to the accompanying drawings.

Inventors: HAYDON GREGORY RICHARD, HAYDON, GREGORY, RICHARD
Applicants: AIRBOSS LTD, HAYDON GREGORY RICHARD, AIRBOSS LIMITED, HAYDON, GREGORY, RICHARD
Application year: 1994
Main classification: B60B25
IPC codes: B60B25, B60C7